This research has the objective of combining the present knowledge of immunogenetics as applied to the major histocompatibility complex, with the technology of separation of different lymphoid cells to further characterize the HLA linkage group. These studies will help to identify alloantigen systems restricted to T lymphocytes, monocytes and B lymphocytes. We intend to study several families in which we have found HLA recombination or HLA-GLO recombinations and HLA-C2 or HLA-Bf recombinations by the HLA-D polymorphism in order to map the complement loci. In another group of experiments utilizing cellular reagents we will investigate functional aspects of T lymphocytes (helper and suppression) following identification of alloantigens on resting T lymphocytes or on activated T lymphocytes. We hope to characterize the HLA-D region into different subregions which may code for help or for suppression of the immune system.